Curable coating compositions such as thermoset coatings are widely used in the coatings art. They are often used as topcoats in the automotive and industrial coatings industry. Color-plus-clear composite coatings are particularly useful as topcoats where exceptional gloss, depth of color, distinctness of image, or special metallic effects are desired. The automotive industry has made extensive use of these coatings for automotive body panels. Color-plus-clear composite coatings, however, require an extremely high degree of clarity in the clearcoat to achieve the desired visual effect. High-gloss coatings also require a low degree of visual aberrations at the surface of the coating in order to achieve the desired visual effect such as high distinctness of image (DOI).
As such, these coatings are especially susceptible to a phenomenon known as environmental etch. Environmental etch manifests itself as spots or marks on or in the finish of the coating that often cannot be rubbed out.
It is often difficult to predict the degree of resistance to environmental etch that a high gloss or color-plus-clear composite coating will exhibit. Many coating compositions known for their durability and/or weatherability when used in exterior paints, such as high-solids enamels, do not provide the desired level of resistance to environmental etch when used in high gloss coatings such as the clearcoat of a color-plus-clear composite coating.
Many compositions have been proposed for use as the clearcoat of a color-plus-clear composite coating, such as polyurethanes, acid-epoxy systems and the like. However, many prior art systems suffer from disadvantages such as coatability problems, compatibility problems with the pigmented basecoat, solubility problems. Moreover, very few one-pack coating compositions have been found that provide satisfactory resistance to environmental etch, especially in the demanding environment of automotive coatings.
It has been found that carbamate functional polymers such as those described in U.S. Pat. No. 5,726,246, U.S. Pat. No. 5,474,811, and U.S. Pat. No. 5,605,965 can be used to provide coating compositions which exhibt significantly improved environmental etch resistance. Carabamate functional polymers have been used to provide commercially advantageous coatings compositions, especially as clearcoats intended for use in composite color-plus-clear coatings.
However, although coating compositions containing carbamate functional polymers generally provide the performance properties currently required by the automotive industry, continuous improvement is always desired. As a result, it would be advantageous to provide improvements in solids or % nonvolatile, flexability, scratch & mar resistance, cold crack resistance, chip resistance and/or the like. At the same time, such improvements must be achieved without any decrease in environmental etch resistance or other commercially required performance property.
It would also be desireable to provide such a technology which would be applicable for use in a wide variety of coating compositions and applications, such as primers, basecoats, clearcoats, two-component systems, anti-chip coating compositions, water borne coatings, solvent borne coatings, coatings for flexible substrates, and the like.
Finally, it would be advantegous to provide improved etch resistant coating compositions which have an increased % NV (nonvolatile) or decreased VOC (volatile organic content) at a sprayable viscosity.
Accordingly, it is an object of the instant invention to provide curable coating compositions which provide all of the advantages of prior art carbamate containing coating compositions, especially good environmental etch resistance, but further exhibit improvement in one or more of the following performance parameters, i.e., flexability, scratch and mar resistance, and/or chip resistance.
It is another object of the invention to provide a technology for improving one or more of the following performance parameters, i.e., % nonvolatile solids, flexability, scratch and mar resistance, and/or chip resistance, in a wide variety of coating compositions and applications, such as primers, basecoats, clearcoats, two-component systems, anti-chip coating compositions, water borne coatings, solvent borne coatings, coatings for flexible substrates, and the like.
It is another object of the invention to provide etch resistance coating compositions which have an increased % NV (nonvolatile) or decreased VOC (volatile organic content) at a sprayable viscosity.